1. Field of the Invention
The present invention relates to maintaining the fundamental physical properties of a liquid alkali metal with dispersed nanoparticles which is such that nanoparticles are uniformly dispersed and mixed in a liquid alkali metal used in heat exchange, cooling and other applications, and suppressing the reaction of the liquid alkali metal with dispersed nanoparticles.
2. Description of the Related Art
Because in general, liquid alkali metals have low melting points, small heat capacities and good heat conductivity, studies are being made in order to use these metals in heat exchangers and as coolants for nuclear energy.
For example, because sodium has high thermal conductivity and for other reasons, this metal is named as a major candidate for the coolant used in a fast-breeder reactor (FBR) system. On the other hand, however, liquid alkali metals including sodium have high chemical reactivity as well as such properties that they can cause severe chemical reactions leading to explosions when they come into contact with air and water.
Therefore, there has been made a proposition to disperse ultra fine particles (nanoparticles: particles whose particle diameters are on the order of nanometers) in a liquid alkali metal, for example, sodium, whereby the high chemical reactivity of sodium is suppressed. For example, Japanese Patent No. 3930495 discloses a liquid alkali metal obtained by dispersing nano-size nickel ultra fine particles in liquid sodium.
However, in this disclosed art, attention is paid only to suppressing the high chemical reactivity of liquid alkali metals, and no discussion is made as to how to maintain various properties expressed by fluidity, viscosity, conductivity, specific heat and the like, which liquid alkali metals essentially have, thereby posing many problems in terms of practical use.
In the following descriptions, liquid metals such as liquid sodium are expressed, for example, as sodium and the like without discrimination between liquid and solid.
As described in the problem of the background art above, the challenge that the present invention takes up is to realize a liquid alkali metal containing uniformly dispersed and mixed nanoparticles, which maintains various properties expressed by fluidity, viscosity, conductivity, specific heat and the like, which liquid alkali metals essentially have, and in which a high chemical reactivity is suppressed.